FIG. 1 shows a prior art differential pressure transducer 100. A first pressure port couples into a first chamber 102, and a second pressure port couples to a second chamber 104. The differential pressure is thereby transferred to diaphragm 108 in the form of a displacement which is measured by displacement sensor 114.
FIG. 2 shows a prior art single-ended pressure transducer 200, which has a pressure inlet 210 coupled to a first chamber 202 which includes generally rigid walls which surround diaphragm 208. A spring 212 provides a resistive pressure, or alternatively, chamber 204 may be filled with a non-hysteresis, temperature neutral fluid, or it may be opened to a neutral pressure environment compared to the pressure to be measured by inlet 210. Displacement sensor 214 measures the diaphragm 208 movement.
In higher pressure applications, the diaphragm 108 of FIG. 1 and diaphragm 208 of FIG. 2 may have a suitable thickness which provides a suitable modulus for the differential pressure in use.
A problem arises in pressure sensors and transducers which utilize fiber optic Bragg gratings, also known as fiber Bragg gratings (FBG), for displacement measurement where the fiber Bragg grating has response coefficients such that the FBG is responsive not only to pressure but also to temperature. This becomes a serious problem in oil and gas exploration, where temperature variations from 25 degrees C. to 200 degrees C. or more are not uncommon. In prior art pressure sensor systems, a per-transducer calibration characteristic has been stored, and a separate temperature sensor is used in combination with the strain reading to compensate for this temperature effect on the pressure measurement.